1. Field of the Invention
This invention relates to a seal ring used for magnetic fluid seal device and its manufacturing method.
2. Description of the Prior Art
There is a magnetic fluid seal devices conventionally known and used practically for magnetic disk devices as shown in FIG. 2 and 3.
This device has been disclosed by the applicant of this invention in the Japanese Utility Model Laid-Open Publication No. 191423/1983.
In FIGS. 2 and 3, symbols are defined in such a manner as 1 for a cylindrical housing, 2 for a shaft mounted on the housing 1 via a bearing 3, R for a seal ring comprising annular pole pieces 4, 5 fixed on an annular magnet 6 at its both end surfaces, said seal ring being fixed with an adhesive onto the inner peripheries of an outer ring 3b of the bearing 3 by means of a seal gap g between pole pieces 4, 5 and an inner ring 3a of the bearing 3. The inner ring 3a is fixed onto the shaft 2 while fixing the outer ring 3b onto the housing 1. The inner ring 3a and pole pieces 4, 5 comprise magnetic substance. Symbol numeral 7 represents a magnetic fluid maintained by a magnetic force in said seal gap g, in other words it is a magnetic fluid maintained by a magnetic field generated by the magnet 6 between the inner ring 3a and seal member C. The device of sealing magnetic fluid comprises said seal ring R and said magnetic fluid 7. Numerals 8 represents a disk engaged in the shaft 2, while denoting a magnetic head by 9, a ball by 10, a ball retainer by 11 and a seal plate by 12. Thanks to such a configuration, the space between the seal ring R and the inner ring 3a is sealed by the magnetic fluid 7 maintained in between both members R and 3a, for preventing the entry of dust created from the bearing (grease dust), etc. into a clean zone. A magnet in said seal ring R used in a conventional device of sealing magnetic fluid is coated (hereinafter referred to as coating) with a resin. This coating aims to prevent magnet dust from entering into a clean zone. For example, when the seal ring R is integrated into HDD motor and the magnet contacts with the housing, magnet powder attaches to the housing This attached dust (the magnet powder) separates by vibration etc. from the housing and attaches to a disk surface, which causes to arise a head crash. Especially in dust from the magnet, the powder has a magnetic nature which causes a magnetic record error and gives rise to some problems.
However, said seal ring R, used in a conventional device of sealing magnetic fluid, due to different kinds between magnet coating agent with resin and adhesive for magnet and pole piece requires a process of covering the magnetic with a resin (hereinafter referred to as coating) and the other process of bonding the coated magnet and the pole pieces using an adhesive, during manufacture. In addition, this bonding process must have divided into 2 subprocesses.
In other words, conventional devices have been manufactured in the following procedures.
(1) First, an annular magnet is coated with a resin (wholly, or magnet inter or outer diameter surface) to manufacture an annular magnet 6 shown in FIG. 4 (a).
(2) This annular magnet 6 is rotated around an axis shown in FIG. 4 (a) and an adhesive 14 is coated on one surface using a dispenser 13, etc., without portions left uncoated.
(3) An annular pole piece 4 is stacked coaxially on the annular magnet 6 coated with the adhesive 14, pressed with a die 15 and both members 4, 6 are bonded together shown in FIG. 4 (b).
(4) The annular pole piece 4 and the annular magent 6, after being bonded into a body, are turned upside down and then the adhesive 14 is coated as shown in FIG. 4 (c) by the method described above on the opposite side (the other side) of the annular magnet 6.
(5) A second annular pole piece 5 is stacked coaxially with the first pole piece 4 on the annular magnet 6 coated with the adhesive, as shown in FIG. 4 (d), pressed with the die 15, thus 3 members 4, 5 and 6 are bonded together.
As described above, according to a conventional methods of manufacturing seal ring R, the first and second bonding processes are required, resulting therefore in many labor man-hours, much labor force and higher manufacturing cost as a matter of disadvantage.